The Atlantoaxial dislocation (AAD) is a fracture of the odontoid process, in such a way that the end that forms a joint with the atlas is separated from its base and kept in position only by the ligaments, which are not strong, joining it to the atlas. Usually AAD presents with occipital pain, others develop vertigo, brainstem signs, lower cranial nerve palsies. The brainstem findings occur with either basilar invaginations or with the alteration of the path of the vertebral artery with changing of normal anatomy.
Though Idiopathic Cervical Dystonia as a sequel to AAD has been reported in literature.  Upper limb dystonia is unusual in such cases and has never been reported from India as well as from any part of world and we report a 19-year-old male with AAD who presented with limb dystonia and hemiparesis
A 19-year-old boy born of a non-consanguineous marriage, following a trivial trauma to the nape of neck before 2 years developed progressive spastic right hemiparesis. Three months prior to admission, he developed urinary urgency, precipitancy and constipation, and abnormal posturing of right upper limb predominantly of the hand.There was history of right hemiparesis when he was four years old, which improved spontaneously over two months. He denied history of fever, accident or vaccination prior to the present illness.
His neurological examination revealed short neck, low hairline and spastic right-sided hemiparesis. There was marked hyper-reflexia and clonus with posterior column impairment without signs of spinothalamic tract involvement. This was associated with restriction of neck movements and neck spasm. There were abnormal movements of right upper limb predominantly distal, in form of repetitive sustained posturing suggestive of dystonia.
The clinical, biochemical and radiological examination revealed neither evidence of rheumatoid arthritis nor any inflammatory, connective tissue disorder. Magnetic Resonance Imaging (MRI) of craniovertebral junction showed a mobile Atlantoaxial dislocation with a well-developed posterior arch of atlas and the absence of the lamina of the axis.The MRI of brain was normal.
Atlantoaxial dislocation (AAD) constitutes an important group of Cranio-Vertebral Junction anomalies frequently requiring emergency decompression and stabilization of joints to prevent morbidity and mortality resulting from compression of neurovascular bundles. Although present since birth, patients become symptomatic at a later age (often in third decade) usually following a trauma. The trauma may be so trivial, so as to be forgotten by the patient himself. When present, the severity of symptoms and its progression bears no relationship to the injury sustained. It is suggested that chronic recurrent trauma during neck movements and daily activities is an important factor for making the illness symptomatic and its sudden aggravation. Because of its varied clinical presentation and an unpredictable course the AAD is often misdiagnosed. Its usual manifestations include nuchal pain and rigidity, progressive cervical myelopathy, foramen magnum syndrome and sudden death due to compression of vital structures at cervico- medullary junction.
Dystonia is a rare neurological disorder characterized by sustained muscle contraction with resultant bizarre muscle movements and hence bizarre posturing. Broadly dystonia can be classified as focal, generalized, early onset or late onset.  Though dystonia due to diverse etiologies like drugs, degenerative diseases like progressive supra nuclear palsy and even cortical oligoastrocytoma have been described.  There has been a frequently reported association between peripheral injuries or pain and subsequent development of dystonia. Although this has been noted for many years, the mechanism is unclear and causative link is speculative. Most cases have been in patients who develop various forms of focal adult onset primary torsion dystonia after local injuries. Some patients may have pre-existing genetic liability to dystonia but this has been unproven. Occasionally Dystonia have been described in surprising clinical settings like spinal cord lesions and brainstem hemorrhage. [4,5] In the contrary, cervical dystonia itself may result in orthopedics and neurological complications including cervical spine degeneration, spondylosis, disk herniation, vertebral subluxation and fractures, radiculopathies and myelopathy.  AAD leading to dystonia could be due to multiple factors like limb pain and cervical cord lesion. Our case report is exceptional and AAD leading to limb dystonia has probably never been described in literature.
The exact mechanism of movement disorders in cervical cord lesions is yet not clearly understood. However, various hypotheses have been proposed which includes altered sensory input, abnormal processing of both input and output signals in the spinal interneurons and increased excitability of the spinal motor neurons. Disruption of the somatosensory pathways or motor cortex to the striatum also may produce abnormal movements without sensory loss.
Hand dystonia in our patient was ascribed to AAD with cord compression because the abnormal movements of hand completely disappeared after the correction of AAD.
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